This invention relates generally to electrical devices for de-gaussing or erasing magnetic recording tapes and pertains more particularly to such systems using electromagnets and structures to move the tape with respect to the electromagnets.
Many types of devices are known in the prior art for erasing magnetic recording tapes. One example is U.S. Pat. No. 2,826,643 to Bruce Greiner, which discloses a method of erasing magnetic tapes by placing the tape between two demagnetizing coils, which are connected in parallel. That patent discloses the use of a threaded rod having a handwheel for moving the two coils towards and away from each other in order to accomodate recording tape of differing widths. That patent also discloses the use of a motor in combination with a roller for use in rotating a magnetic tape roll by contacting the roll on its outer circumference.
Another example of a prior art tape de-gausser is Rettinger U.S. Pat. No. 2,730,570 which shows the use of a pair of oppositely mounted "E" shaped magnetic cores for erasing a length of magnetic tape. From FIG. 2 of that patent, it appears that the sections of the magnetic cores have slightly narrowed tips.
The major purpose of bulk magnetic tape eraser or degausser machines is to effectively remove information which has been magnetically encoded onto magnetically sensitive tape which is stored on reels, cassettes, or some other form of cartridge or container. It is desireable that such tape may be erased quickly in bulk, while it is still on the reel or cartridge in which it is normally stored. For example, it is desireable that reels of magnetic video tape for television use can be quickly erased and reused to record new video signals without encountering any latent remains of previously recorded video signals. Such tape erasers are valuable for use in erasing video tapes, audio tapes, and computer tapes.
It is desireable that magnetic tape erasers be capable of erasing tapes stored on the large variety of reels, cassettes, and cannisters which are in commercial use without removing the tape from its container. It is also desireable that magnetic tape erasers be capable of adequately and fully erasing modern high-coercivity tapes made using chromium or other metals. Because of higher recent performance standards for magnetic recording tapes, it is important that magnetic tape erasers make as complete as possible an erasure of information encoded on a tape so as to prevent remnant information of prior recordings from contaminating later recordings.
A problem with prior art tape erasers is their inability to efficiently, effectively, and quickly erase high coercivity magnetic recording tapes. Another problem with prior art tape erasers is their inability to accurately, easily, reliably, and quickly adjust to accomodate different sizes and shapes of magnetic tape containers. A further problem with prior art tape erasers is their requirement of manual operator efforts in the tape erasing process.